Alega sits in one of the least-written-about corners of the Pacific. The books below won't all be about American Samoa specifically, but each one will give a traveller a richer sense of the place they are in.
Coming of Age in Samoa by Margaret Mead (1928). Mead's field research was conducted in Ta'ū, one of the Manu'a islands of American Samoa, and this book became one of the most influential anthropological studies of the twentieth century. The science has been contested, but as a portrait of Samoan fa'a Samoa — the ceremonial life, the rhythms of a village, the role of the matai — it remains vivid and thought-provoking. Read it before you come; read Derek Freeman's later rebuttal if you want the argument.
The Happy Isles of Oceania by Paul Theroux (1992). Theroux paddled a kayak across a large portion of the Pacific and wrote about it with his usual mixture of candour, irritability, and genuine curiosity. His chapters on Samoa — he visited both the American and independent halves — are among the most honest short portraits of contemporary Pacific island life written for an outsider audience. He is not always right, but he is never dull.
Leaves of the Banyan Tree by Albert Wendt (1979). The first great novel of the Pacific in English, written by a Samoan. Wendt traces three generations of a Samoan family through the colonial and post-independence era, following the fractures that run through fa'a Samoa as money and Christianity and modernity press in from outside. Wendt is from independent Samoa, not American Samoa, but the cultural world he describes is the same one you will encounter in Alega.
The Piano in a Clearing by Sia Figiel (2010, stories). Figiel is another Samoan writer whose fiction inhabits the interior life of village and family and the complicated pressures on women in traditional Pacific society. Her shorter work is more accessible than her celebrated debut novel; any of her collections will recalibrate the way you look at the village around you.